1. Field of the Invention
The present invention generally relates to a claw-pole electric generator and a bicycle electric generator hub that uses the same.
2. Background Information
Bicycle electric generator hubs that use claw-pole electric generators are known in the art. In some conventional claw-pole electric generators, a yoke is configured from a plurality of first and second stacked yokes obtained by stacking plate-shaped pieces. The conventional claw-pole electric generators configured from stacked yokes include those in which the plate-shaped pieces are formed into a C shape and have a yoke internal peripheral part, a yoke external peripheral part and a core part connecting the two. (See, for example, Japanese Patent Application Laid-Open No. 2001-202017.).
In this conventional electric generator, the first and second stacked yokes are mounted on a hub axle. The first and second stacked yokes are inserted in alignment with a circumferential direction into a plurality of yoke mounting grooves formed to the width of the first and second stacked yokes at either ends of a coil. The first and second stacked yokes are disposed alternately so that distal ends of the yoke external peripheral parts of the stacked plate-shaped pieces overlap and face opposite directions.
The conventional claw-pole electric generators configured from stacked yokes may also include plate-shaped pieces that have a disc part and a yoke external peripheral part that extends in a radial pattern from a peripheral edge of the disc part. The yoke external peripheral part bends toward a direction intersecting with the disc part. (See, for example, Japanese Patent Application Laid-Open No. 2004-229403.)
In this conventional electric generator, the first and second stacked yokes are mounted so that the disc parts of the stacked plate-shaped pieces are in alignment with an axial direction of the hub axle at both ends of the coil. The first and second stacked yokes are disposed alternately so that distal ends of the yoke external peripheral parts face opposite directions.
In either of the electric generators, the yoke external peripheral parts are disposed to allow a small gap to be formed in relation to a permanent magnet fixed in place on a hub shell in order to increase power generating efficiency. When the yoke is configured from these alternately disposed first and second stacked yokes, output loss due to eddy currents is reduced and the output characteristics are improved.
In the former conventional electric generator, the plate-shaped pieces of the stacked yoke may become misaligned from the radial direction of the hub axle. In the latter conventional electric generator, if the angles of curvature of the yoke external peripheral parts differ even slightly, the external peripheral surface of the yoke may be uneven as a result.
In either of these conventional electric generators, since the external peripheral parts of the stacked yokes are disposed to allow a small gap with the magnet, the external peripheral parts of the plate-shaped pieces may come into contact with the magnet if an external peripheral surface of the yoke becomes misaligned and uneven. Therefore, hardening a portion fixed to the hub axle that includes the yoke with a synthetic resin by insert molding or another such method has been considered as a solution to prevent these problems. However, if such a solution is employed, the weight of the fixed portion increases proportionate to the resin, causing a weight increase in the electric generator.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved claw-pole electric generator that ensures the yoke does not contact the magnet. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.